User Adaption layers

M2UA (MTP Level 2 User Adaption)

What is SIGTRAN ?SIGTRAN Its a protocol suite used to carry PSTN signalling (SS7, ISDN, TUP and SCCP etc.) over SCTP as a Transport protocol in an IP network developed by IETF group called SIGTRAN Working Group.

Sigtran working group Purpose is to address the transport of packet-based PSTN signaling over IP Networks by considering functional and performance requirements of the PSTN signaling.

History of SIGTRANThe main difference between these two schemes (i.e PSTN and IP) is that the long distance carrier is replaced by an IP network. So we convert a long distance call into two local calls plus long distance IP transport. Thus the IP Telephony Service Provider (ITSP) can offer a cheaper price to its customers. The costs of transporting the speech using an IP network are lower than those of a long distance carrier, as the whole facilities are shared among all the users and there is no dedicated channels. If we have a dedicated full-duplex circuit to transmit a

telephone conversation we make poor use of it, as most of the time at least one of theparties will be silent (at least that is the idea) and its channels unused.

Architecture View of SIGTRAN

In the SIGTRAN architecture view, gateways connect the SS7 and IP networks. We can identify the three elements carrying PSTN signalling over IP network i.e. MG, SG and MGC. The SS7-IP gateways translates and transport the SS7 signaling through the IP network, Both the media data and the signaling can traverse the IP network and reach the destination, providing the same kind of services that the PSTN offers while making a better use of the network that carries the voice stream. Media Gateway (MG) - The media gateway converts media provided PSTN network to the format required in IP network .eg. Media Gateway terminates PSTN media streams, packetizes the voice and delivers the packets to the IP network. At the receiver side, it performs the reverse function. Signaling Gateway (SG) - The Signalling gateway receives and translates signalling from Pstn network and send accross IP network and vice-versa. Media Gateway Controller (MGC) - Controls the parts of the call state that pertain to connection control for media channels in a MG i.e registration and resource management at MG.

IP SCP (IP enabled Service Control Point) - This exists wholly within the IP network, but is addressable from the SS7 network.

SS7 SIGTRAN Call Scenario

SIGTRAN Protocol Stack

User Adaption Layers

To make SS7 or ISDN or TCAP signaling transport over IP networks possible, an SS7-IP gateway must provide the means for translating SS7 messages into IP datagrams, and vice-versa. However, that translation can be done at several layers. Even though there is no need to provide translation at all levels in the SS7 stack, adaptation modules ( Layers) are developed that can translate SS7 signaling at the SCCP level, as well as MTP3 and MTP2 (there are even two proposals for MTP2)

User Adaption Layers...

M3UA (MTP3-User Adaptation Layer) The MTP3-User Adaptation Layer (M3UA) works at a lower layer than SUA. It directly replaces MTP3, and it provides support for the transfer of all SS7 MTP3-User Part messages, such as ISUP or SCCP

over IP using SCTP.

M2UA (MTP2-User Adaptation Layer) MTP2 level we have two different protocols that translates SS7 into IP. One of them is the MTP2-User Adaptation Layer (M2UA) and the other is MTP2-User Peer-to-Peer Adaptation Layer (M2PA). They both replace the MTP2 protocol, adapting the MTP3 protocol to the SCTP/IP stack. IUA (ISDN Q.921-User Adaptation Layer) The ISDN Q.921-User Adaptation Layer (IUA). The ITU-T recommendation Q.921 defines the data link level protocol used in ISDN signaling, also known as the Link Access Procedures on the D-channel (LAPD). IUA replaces Q.921 and uses SCTP as the transport layer, and provides transparent adaptation to Q.921 users, such as Q.931.

User Adaption Layers...

SUA (SCCP-User Adaptation Layer) The SCCP-User Adaptation Layer (SUA) is a protocol designed to transport any SCCP-User signaling (such as TCAP) over IP using SCTP, in a seamless way. SUA can be used between a Signaling Gateway (SG) and an IP signaling endpoint (a Service Switching Point (SSP) or Service Control Point (SCP)), but can also provide transport of SCCP user information directly between IP endpoints rather than through a SG. The SG is needed only to assure interoperability with SS7 signaling in the

switchedcircuit network. It also supports all the features SCCP protocol supports in the IP network.Nodal Interworking Function (NIF) Basically, the NIF serves as an interface between PSTN stack layers and Adoption layers within the

SG.

Conversion happening at Signaling Gateway

SCTPSCTP is a reliable connection-oriented, multi-homing, multi-streaming transport protocols used to carry the application data in an IP network. SCTP is designed to transport Public Switched Telephone Network (PSTN) signaling messages over IP networks, but is capable of broader applications by SIGTRAN group to overcome the limitations of TCP such as Head-of-line blocking, Multi-homing and Sync attacks etc.

Replaces high cost traditional circuit-switched network with the cheaper IP network.Sigtran associations are capable of delivering high bandwidth in a single connection. Using SIGTRAN protocols the application vendor like SMSC, HLR, ASG, can support heavy SS7 traffic.

Call Trace View isolates call specific information such as status of each call (active/ completed), duration of completed call, OPC, DPC, CIC, Called and Calling Party Numbers, and more. Search and filtering capabilities for both real-time as well as offline analysis. Provides the 'Capture Filter' option to filter M2UA, M2PA, M3UA and SUA frames on the specified ports.

ISUP ITU ISUP Conformance testing ISUP ANSI M3UA ITU

MAPS - SS7 SIGTRAN Configuration

Scenario: MAPS acting as Signaling Gateway

Scenario: MAPS acting as Softswitch

Testing over IP

SS7 SIGTRAN Call Scenario

Testing over IP

MAPS - SS7 SIGTRAN Call Generation & Reception

MAPS ISDN SIGTRAN Emulator (PKS135)

38

MAPS ISDN - SIGTRAN (PKS135)

MAPS ISDN SIGTRAN Key Features

Simulates ISDN signaling over IP (ISDN-SIGTRAN) Generates and process all ISDN messages such as Setup, Connect, Release messages, and more Switch and Subscriber Emulation User controlled access to optional ISDN parameters such as timers Provides various release cause codes such as rejected, no user response, user busy, congested, and so on to troubleshoot the problems in ISDN Impairments can be applied to messages to simulate error conditions Supports scripted call generation and automated call reception.